feat: add Stirling-PDF-style layout with sidebar, tool panel, dropzone, and theme toggle

apps/web/src/components/layout/app-layout.tsx

@@ -0,0 +1,30 @@
+import { useState } from "react";
+import { Sidebar } from "./sidebar";
+import { ToolPanel } from "./tool-panel";
+import { Footer } from "./footer";
+import { Dropzone } from "../common/dropzone";
+
+interface AppLayoutProps {
+  children?: React.ReactNode;
+  showToolPanel?: boolean;
+}
+
+export function AppLayout({ children, showToolPanel = true }: AppLayoutProps) {
+  const [_settingsOpen, setSettingsOpen] = useState(false);
+
+  return (
+    <div className="flex h-screen bg-background text-foreground overflow-hidden">
+      <Sidebar onSettingsClick={() => setSettingsOpen(true)} />
+      {showToolPanel && <ToolPanel />}
+      <main className="flex-1 flex flex-col overflow-hidden">
+        <div className="flex-1 overflow-y-auto p-6 flex items-center justify-center">
+          {children || <Dropzone />}
+        </div>
+        <div className="text-center text-xs text-muted-foreground py-2 border-t border-border">
+          Privacy Policy
+        </div>
+      </main>
+      <Footer />
+    </div>
+  );
+}